The grades on a history midterm at Gardner Bullis are normally distributed with $\mu = 66$ and $\sigma = 4.5$. Ashley earned a $60$ on the exam. Find the z-score for Ashley's exam grade. Round to two decimal places.
A z-score is defined as the number of standard deviations a specific point is away from the mean We can calculate the z-score for Ashley's exam grade by subtracting the mean $(\mu)$ from her grade and then dividing by the standard deviation $(\sigma)$ $ { z = \dfrac{x - {\mu}}{{\sigma}}} $ $ { z = \dfrac{60 - {66}}{{4.5}}} $ ${ z \approx -1.33}$ The z-score is $-1.33$. In other words, Ashley's score was $1.33$ standard deviations below the mean.